Analysis of Semantic Embedded IPv6 Address Schemas
Author(s): Yang Bo, Qiong Sun, Tianle Yang, Sheng Jiang, Ian Farrer
This informational document discusses the use of embedded semantics within IPv6 address schemas. Network operators who have large IPv6 address space may choose to embed some semantics into their IPv6 addressing by assigning additional significance to specific bits...
Network Working Group S. Jiang, Ed. Internet-Draft Huawei Technologies Co., Ltd Intended status: Informational Q. Sun Expires: January 16, 2014 China Telecom I. Farrer Deutsche Telekom AG Y. Bo Huawei Technologies Co., Ltd T. Yang China Mobile July 15, 2013 Analysis of Semantic Embedded IPv6 Address Schemas draft-jiang-semantic-prefix-06 Abstract This informational document discusses the use of embedded semantics within IPv6 address schemas. Network operators who have large IPv6 address space may choose to embed some semantics into their IPv6 addressing by assigning additional significance to specific bits within the prefix. By embedding semantics into IPv6 prefixes, the semantics of packets can be easily inspected. This can simplify the packet differentiation process. However, semantic embedded IPv6 address schemas have their own operational cost and even potential pitfalls. Some complex semantic embedded IPv6 address schemas may also require new technologies in addition to existing Internet protocols. The document aims to understand the usage of semantic embedded IPv6 address schemas, and neutrally analyze on the associated advantages, drawbacks and technical gaps for more complex address schemas. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Jiang, et al. Expires January 16, 2014 [Page 1] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 This Internet-Draft will expire on January 16, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Understanding of Semantic IPv6 Prefix Address Schema . . . . 4 3.1. Overview of Semantic IPv6 Prefix Address Schema . . . . . 4 3.2. Existing Approaches to Traffic Differentiation . . . . . 5 3.3. Justification for Semantics with the IPv6 Prefix . . . . 6 3.4. The Semantic Prefix Domain . . . . . . . . . . . . . . . 7 3.5. The Embedded Semantics . . . . . . . . . . . . . . . . . 8 3.6. Network Operations Based on Semantic Prefixes . . . . . . 8 4. Potential Benefits . . . . . . . . . . . . . . . . . . . . . 9 5. Potential Drawbacks . . . . . . . . . . . . . . . . . . . . . 10 6. Gaps for complex semantic prefix scenarios . . . . . . . . . 11 6.1. Semantic Notification in the Network . . . . . . . . . . 11 6.2. Semantic Relevant Interactions between Hosts and the Network . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.3. Additional Technical Extensions . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Change Log (removed by RFC editor) . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11.1. Normative References . . . . . . . . . . . . . . . . . . 15 11.2. Informative References . . . . . . . . . . . . . . . . . 15 Appendix A. An ISP Semantic Prefix Example . . . . . . . . . . . 15 A.1. Function Type Semantic Bits . . . . . . . . . . . . . . . 16 A.2. Network Device Type Bits within Network Device Address Space . . . . . . . . . . . . . . . . . . . . . . . . . . 17 A.3. Subscriber Type Bits within Subscriber Address Space . . 17 A.4. Service Platform Type Bits within Service Platform Jiang, et al. Expires January 16, 2014 [Page 2] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 Address Space . . . . . . . . . . . . . . . . . . . . . . 18 Appendix B. An Enterprise Semantic Prefix example . . . . . . . 19 Appendix C. A Multi-Prefix Semantic example . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction As the global Internet expands, it is being used for an increasingly diverse range of services. These services place differentiated requirements upon packet delivery networks meaning that Internet Service Providers and enterprises need to be aware of more information about each packet in order to best meet a specific service's needs. Dividing a network into different subnets according to different semantics is already widely existing today, mostly motivated by either topological aspects, logical user/device groups, and/or trust/security domains. In order to inspect the semantics of packets so that they can be treated differently, some network operators have chosen to embed semantics into IPv6 prefixes. Routers and other intermediary devices can easily apply relevant policies as required. User types, service types, applications, security requirements, traffic identity types, quality requirements and other criteria may be used according to how a network operator may want to differentiate its services. Packet- level differentiation can also enable flow-level and user-level differentiation. Consequently, the network operators can treat network packets differently and efficiently. It is believed this mechanism can simplify the management and maintenance of networks. However, semantic embedded IPv6 address schemas come with their own operational cost and even pitfalls. Some complex semantic embedded IPv6 address schemas may also require technologies additional to existing Internet protocols. While network operators, who already have large IPv6 address space allocations, are free to plan and deploy addressing in their preferred way (including semantic embedded IPv6 address schemas), it is useful to analyze the benefits and drawbacks of a semantic approach to addressing. The document only discusses the usage of semantics within a single network, or group of interconnected networks which share a common addressing policy, referred to as a Semantic Prefix Domain. Jiang, et al. Expires January 16, 2014 [Page 3] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 This document does not intend to suggest the standardization of any common global semantics. It does not intend to draw any conclusions, either recommending this kind of address schemas or not. It aims to provide network operators with relevant information to use in the creation of their own addressing policy. 2. Terminology The following terms are used throughout this document: Semantic Prefix: A flexible-length IPv6 prefix which embeds certain semantics. Semantic Prefix Domain: A portion of the Internet over which a consistent semantic-prefix based policy is in operation. Semantic Prefix Policy: A policy based on the embedded semantics within IPv6 prefix. 3. Understanding of Semantic IPv6 Prefix Address Schema Some network operators (either ISPs or enterprise network operators), who have large IPv6 address space, have chosen to embed certain pre- defined semantics into their IPv6 address schemas by assigning additional significance to specific bits within the prefix. The IPv6 addresses of each packet can then explicitly express semantics. Consequently, intermediate devices can easily apply relevant packet differentiating operations accordingly. This mechanism may divert much network complexity to the planning and management of IPv6 addressing and IP address based policies. For illustrations of how semantic prefixes could be applied in real- world scenarios, Appendix A describes an ISP example semantic IPv6 prefix address schema; Appendix B introduces an enterprise semantic IPv6 prefix example; and Appendix C introduces an enterprise example in which a multiple-site enterprise network with several prefixes of different lengths is organized as a single, contiguous Semantic Prefix Domain. 3.1. Overview of Semantic IPv6 Prefix Address Schema Jiang, et al. Expires January 16, 2014 [Page 4] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 A network operator first plans their IPv6 address schema, in which useful semantics (see Section 3.5) are embedded into prefix. They then delegate prefixes with the corresponding semantics to users. The users generate their IPv6 addresses based on assigned prefixes. Then, when the IPv6 stack on the user devices forms packets, the source addresses comprise compliance semantics. For trust reasons, the filters on the edge router may drop packets which are not compliant with assigned prefixes. The embedded semantics are only meaningful within a network domain which implements a single policy (see Section 3.4). Different service providers may make very different choices regarding the specific semantics which are relevant to their networks. Therefore, it is not possible or even desirable to attempt to standardize a general semantic prefix policy. Forwarding policies, access control lists, policy-based routing, security isolation and other network operations (see Section 3.6) can be easily applied according to semantics, which are self-expressed by the source address of every packet. Also, the semantics of the destination address may be taken in account if the destination is in the same Semantic Prefix Domain or the peer Semantic Prefix Domain whose semantics has been notified. 3.2. Existing Approaches to Traffic Differentiation There are several existing approaches which have been developed that can assist operators in identifying and marking traffic. These solutions were mainly developed in the IPv4 era, where the IP address is used as a host locator and little else. The limited capacity of a 32-bit IPv4 address provides very little room for encoding additional information. Correspondingly, these approaches are indirect, inefficient and expensive for operators. 3.2.1. Differentiated Services Quality of Service (QoS) based on and Differentiated Services [RFC2474] is a widely deployed framework specifying a simple and scalable coarse-grained mechanism for classifying and managing network traffic. But in a service provider's network, DiffServ codepoint (DSCP) values cannot be trusted when they are set by the customer as these are arbitrary values. In real-world scenarios, ISPs deploy "remarking" points at the customer edge of their network, re-classifying received packets by rewriting the DSCP field according to local policy using information such as the source/destination address, IP protocol number and transport layer source/destination ports. Jiang, et al. Expires January 16, 2014 [Page 5] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 The traffic classification process leads to increased packet processing overhead and complexity at the edge of the service provider's network. DSCP mechanism abstracts all the semantics into a single-dimension service classes. This abstract processing has lost a lot of semantic information, which providers want to inspect for every packet, then process the packet accordingly. The DSCP in the IPv6 header traffic class field allows 6-bits for encoding service provider specific information related to the contents of the packet. Whilst this is a useful part of an overall packet differentiation architecture, the relative small number of available bits (when compared to the available number of bits within the service providers prefix) means that it cannot be used in isolation. 3.2.2. Deep Packet Inspection Deep Packet Inspection (DPI) may also be used by ISPs to learn the characteristics of users packets. This involves looking into the packet well beyond the network-layer header to identify the specific application traffic type. Once identified, the traffic type can be used as an input for setting the packet's DSCP or other actions. But DPI is expensive both in processing costs and latency. The processing costs means that dedicated infrastructure is necessary to carry out the function. The incurred latency may be too much for use with any delay/jitter sensitive applications. As a result, DPI is difficult for large-scale deployment and it's usage is usually limited to small and specific functions in the network. In short, it is not scalable, and cannot support realtime network operations. 3.3. Justification for Semantics with the IPv6 Prefix Although the interface identifier portion of an IPv6 address has arbitrary bits and extension headers can carry significantly more information, these fields can not be trusted by network operators. Users may easily change the setting of interface identifier or extension headers in order to obtain undeserved priorities/ privileges, while servers or enterprise users may be much more self- restricted since they are charged accordingly. With proper access control filters deployed, the prefix can be trusted by the network operators and is simple to inspect in the IP header of a packet. The packets with the noncompliance source addresses should be filtered. The prefix is delegated by the network and therefore the network is able to detect any undesired Jiang, et al. Expires January 16, 2014 [Page 6] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 modifications and filter the packet accordingly. This also makes it possible for the service provider to increase the level of trust in a customer-generated packet. If the packet has an source or destination address which is outside of the network operator's policy then a session will simply fail to establish. 3.4. The Semantic Prefix Domain A Semantic Prefix Domain is a portion of the Internet over which a consistent set of semantic-prefix-based policies are administered in a coordinated fashion. It is analogous to a Differentiated Services Domain [RFC2474]. Some of the characteristics that a single Semantic Prefix Domain could represent include: a. Administrative domains b. Autonomous systems c. Trust regions d. Network technologies e. Hosts f. Routers g. User groups h. Services i. Traffic groups j. Applications A Semantic Prefix Domain has a set of pre-defined semantic definitions, which are only meaningful locally. Without an efficient semantics notification, exchanging mechanism or service agreement, the definitions of semantics are only meaningful within local Semantic Prefix Domain. Agreements on definitions between network operators could be made. However, this may involve trust models among network operators. Sharing semantic definition among Semantic Prefix Domains enables more semantic based network operations. An enterprise Semantic Prefix Domain may span several physical networks and traverse ISP networks. However, when an interim network is traversed (such as when an intermediary ISP is used for interconnectivity), the relevance of the semantics is limited to network domains that share a common Semantic Prefix Policy. Jiang, et al. Expires January 16, 2014 [Page 7] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 If an ISP has several non-contiguous address blocks, they may be organized as a single Semantic Prefix Domain if the same Semantic Prefix Policy is shared across these non-contiguous address blocks. 3.5. The Embedded Semantics The size of the operator assigned prefix means that there is potentially much more scope for embedding semantics than has previously been possible. The following list describes some suggested semantics which may be useful to network operators besides source/destination location: a. User types b. Applications c. Security domain d. Traffic identity types e. Quality requirements f. Geo-location The selection of semantics varies among different network operators. They may choose one or more semantics to be embedded into their IPv6 address schemas, depending on what is important for them and what may trigger packet differentiation processes in their networks. The selection criterion and the impact of each choice are out of scope of this document. 3.6. Network Operations Based on Semantic Prefixes From the explicit semantics contained within the addresses of each packet, many network operations can be applied. Compared with traditional operations, these operations are easier to realize and stable. Although detailed operation vary depending on various embedded semantics, the network operations based on semantic prefix can be abstracted into following categories: a. Statistic based on certain semantic. Any embedded semantic can be set as a statistic condition. In other words, any embedded semantic can be measured independently. b. Differentiate packet processing. Many packet processing operations can be applied based on the semantic differentiation, such as queueing, path selection, forwarding to certain process devices, etc. Jiang, et al. Expires January 16, 2014 [Page 8] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 c. Security isolation. A set of packet filters that are based on semantic can fulfil network security isolation. d. Access control. Resource access, authentication, service access can be directly based on semantics. e. Resource allocation. Resources, such as bandwidth, fast queue, caching, etc., can be allocated or reserved for certain semantic users/packets. f. Virtualization. Within a Semantic Prefix Domain, organizing virtual networks is simplified by assigning all the nodes the same semantic identifier so that the packets from them can be distinguished from other virtual networks. It should also be noticed that these operations do not have to be processed on the same single device. They may be separated among network devices. In other words, if there are multiple semantics in a Semantics Prefix Domain, various semantics may be understood and treated on different network devices. It is not necessary for all network devices in such domain to capable of understanding all semantics. 4. Potential Benefits Depending on various embedded semantics, different beneficial scenarios can be expected. a. Semantic prefix address schema provides a directly and explicitly mechanism for packet inspection. It improves the inspecting efficiency on IPv6 network devices. b. Simplified measurement and statistics gathering: the semantic prefix provides explicit identifiers which can be used for measurement and statistical information collection. This can be achieved by checking certain bits of the source and/or destination address in each packet. c. Simplified flow control: by applying policies according to certain bit values, packets carrying the same semantics in their source/destination addresses can. d. Service segregation: when service related information is encoded within the semantic prefix, this can be used to create simple access-control lists which can be applied uniformly across all network devices. Security zones are such typical services that need to be segregated. Jiang, et al. Expires January 16, 2014 [Page 9] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 e. Policy aggregation: the semantic prefix allows many policies to be aggregated according to the same semantics within the policy based routing system [RFC1104]. f. Easy dynamic reconfiguration of semantic oriented policy: network operators may want to dynamically change the policy actions that are operated on certain semantic packets. The semantic prefix allows such changes be operated easily, as only a small number of consistent policy rules need to be updated on all devices within the semantic prefix domain. g. Application-aware routing: embedding application information into IP addresses is the simplest way to realize application aware routing. h. Easy user behavior management: based on the user type reading from the addresses, any improper user behaviors can be easy detected and automatically handle by network policies. i. Easy network resources access rights management: the authentication of access right may already be embedded into the addresses. Simple matching policies can filter improper access requests. j. Easy virtualization: virtual network based on any semantics can be easily deployed using the semantic prefix mechanism. 5. Potential Drawbacks a. Address consumption caused by lower address utility rate. Embedding semantics into IPv6 addresses causes the network to use more of the address space that it normally would. The wastage comes from aligning. 1) A small addressing requirement for a separate type may get the same large address space as a large addressing requirement. 2) The number of types in each semantic has to align to 2^n, for example, 5 types uses to take 3 bits in the prefix. Network operators should be aware they may not get more addresses because they have allocated their assigned address block(s) for semantic use without the addresses actually being in use - leading to a lower address utility rate. Although the current Regional Internet Registry (RIR) policies do not disallow such address usage, such usage has not been taken into account in calculating reasonable addressing quotients. b. Complexity that is created within the semantic prefix policy. Encoding too many semantics into prefixes can come at the expense Jiang, et al. Expires January 16, 2014 [Page 10] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 of future addressing flexibility. At the same time, embedding too many semantics may induce semantic overlap. Careful consideration should be taken with semantics definition. c. The risk of privacy/information leakage. The semantics in the address may be guessable, or leaked to outside the organisation. Therefore, some information of either subscribers or networks may be leaked, too. d. Burdening the host OS. In some complex semantic prefix scenarios, the semantics prefix mechanism puts extra burden on the originator. In such scenarios, host devices are given multiple IPv6 prefixes and required to choose correctly. When forming a packet, the originator of packets (normally the host OS) has to pick the right address/prefix according to the semantics to access a service. e. In order to perform policies based on trusted user/prefix, tight/ strict access control filter linked with prefix assignment is requested. It is the filter who makes sure the prefix right. The filter should link back to other states of the user, like user authentication, etc, in order to match the packet to its properties and check whether it is mapped to right semantics or not. 6. Gaps for complex semantic prefix scenarios The simplest semantic prefix model is to embed only abstracted user type semantics into the prefix. Current network architectures can support this semantic prefix model, in which each subscriber is still assigned a single prefix, while they are not notified the semantic embedded in the prefix. In order to fulfill more benefits of the semantic prefix design, additional functions are needed to allow semantic relevant operations in networks and semantic relevant interactions with hosts. IPv6 provides a facility for multiple addresses to be configured on a single interface. This creates a precondition for the approach that user chooses addresses differently for different purposes/usages. 6.1. Semantic Notification in the Network In order to manage semantic prefixes and their relevant network actions, the network should be able to notify semantics along with prefix delegation. Jiang, et al. Expires January 16, 2014 [Page 11] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 When an prefix is delegated using a DHCPv6 IA_PD [RFC3633], the associated semantics should also be propagated to the requesting router. This is particularly useful for autonomic process when a new device is connected. 6.2. Semantic Relevant Interactions between Hosts and the Network The more that semantics are embedded into a prefix, the more complicated functions are needed for semantic relevant interactions between hosts and the network, such as prefix delegation, host notification, address selections, etc. In practice, a single host may belong to multiple semantics. This means that several IPv6 addresses are configured on a single physical interface and should be selected for use depending on the service that a host wishes to access. A certain packet would only serve a certain semantic. The host's IPv6 stack must have a mechanism for understanding these semantics in order to select the right source address when forming a packet. If the embedded semantic is application relevant, applications on the hosts should also be involved in the address choosing process: the host IPv6 stack reports multiple available addresses to the application through socket API (one example is "IPv6 Socket API for Source Address Selection" [RFC5014]). The application then needs to apply the semantic logic so that it can correctly select from the offered candidate addresses. Although [RFC6724] provides an algorithm for source address selection, some semantic prefix policies may conflict with this algorithm. In this case, source address selection mechanisms may need further supporting functions to be developed. 6.3. Additional Technical Extensions There are several areas in which the semantic prefix could be extended in order to increase the usefulness and applicability of the semantic prefix address schema. They are listed here for future study. Currently, their feasibility, usefulness and applicability are not carefully studied yet. - Dynamic Policy Configuration Dynamic policy configuration would simplify the distribution of policy across devices in the semantic prefix domain. New functions or protocol extension are needed to enable dynamic changes to the policy actions in operation on certain semantic packets. Jiang, et al. Expires January 16, 2014 [Page 12] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 - Semantics Announcements to peer networks A network may announce all, or some of its Semantic Prefix Policy to connected peer networks. This could be used to enable more dynamic configuration and enable traffic from different semantic prefix domains to traverse different networks whilst having the same semantic prefix policy applied. To achieve this automatically by message exchanging would require new functions or protocol extensions. - Extension of Prefix Semantics beyond the left-most 64 bits The prefix concept refers here to the left-most bits in the IP addresses delegated by the network management plane. The prefix could be longer than 64-bits if the network operators strictly manage the address assignment by using Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315] (but in this case standard StateLess Address AutoConfiguration - SLAAC [RFC4862] cannot be used). - Organizing consumer/home networks according to semantics Consumers or subscribers are currently assigned /48 or /56 prefixes. They have bits, which may also count the right-most 64 bits too, to organize their networks into subnets. These subnets may be organized according to some semantics that are meaningful for the user himself. In such scenario, the user acts as the network operator for his own network. Some additional tecnologies/functions may be needed to make such organizing and follow-up management efficient. 7. IANA Considerations This document has no IANA considerations. 8. Change Log (removed by RFC editor) draft-jiang-semantic-prefix-04: add new pitfalls section; restructure to be a neatrul analysis document; 2013-07-15. Jiang, et al. Expires January 16, 2014 [Page 13] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 draft-jiang-semantic-prefix-05: reword to emphasis this mechanism is a (not the) method that network operators use their addresses; add text to clarify the increased trust is actually from the deployment of source address filter, which is a compliance requirement by semantic prefix; restructure the document, move examples and gap analysis into appendixes, reorganize most content into a frame section; add summarized description for framework at the beginning of Section 3; add description for network operations based on semantic prefix; add a new coauthor who contributes an enterprise semantic prefix network example; combine most of draft-sun-v6ops-semantic- usecase into the draft as ISP example in appendix; 2013-5-28. draft-jiang-semantic-prefix-04: add new coauthor, re-organize the content, and refine the English, 2013-1-31. draft-jiang-semantic-prefix-03: add the concept of hierarchical Semantic Prefix Domain and more gap analysis, 2012-10-22. draft-jiang-semantic-prefix-02: resubmitted to v6ops WG. Removed detailed examples and recommendations for semantics bits, 2012-10-15. draft-jiang-semantic-prefix-01: added enterprise considerations and scenarios, emphasizing semantics only for local meaning and no intend to standardize any common global semantics, 2012-07-16. 9. Security Considerations Embedding semantics in prefix is actually exposing more information of packets explicit. These informations may also provide convenient for malicious attackers to track or attack certain type of packets. If networks announce their local prefix semantics to their peer networks, it may also increase the vulnerable risk. Prefix-based filters should be deployed, in order to protect against address spoofing attacks or denial of service for packets with forged source addresses. 10. Acknowledgements Useful comments were made by Erik Nygren, Dan Wing, Nick Hilliard, Ray Hunter, David Farmer, Fred Baker, Joel Jaeggli, John Curran, Tim Chown, Ted Lemon, Owen DeLong, Lorenzo Colitti, George Michaelson, Joel Halpern, Vizdal Ales, Bless Roland, Manning Bill, Manfred Albert and other participants in the V6OPS working group. 11. References Jiang, et al. Expires January 16, 2014 [Page 14] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 11.1. Normative References [RFC1104] Braun, H., "Models of policy based routing", RFC1104, June 1989. [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC2474, December 1998. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC3315, July 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC3633, December 2003. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC4291, February 2006. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC4862, September 2007. [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, "Default Address Selection for Internet Protocol Version 6 (IPv6)", RFC6724, September 2012. 11.2. Informative References [RFC5014] Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6 Socket API for Source Address Selection", RFC5014, September 2007. Appendix A. An ISP Semantic Prefix Example This ISP semantic prefix example is abstracted from a real ISP address architecture design. Note: for now, this example only covers unicast address within IP Version 6 Addressing Architecture [RFC4291]. For ISPs, several motivations to use semantic prefixes are as follows: a. Network Device management: Separated and specialized address space for network device will help to identify the network device among numerous addresses and apply policy accordingly. Jiang, et al. Expires January 16, 2014 [Page 15] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 b. Differentiated user management: In ISPs' network, different kinds of customers may have different requirements for service provisioning. c. High-priority service guarantee: Different priorities may be divided into apply differentiated policy. d. Service-based Routing: ISPs may offer different routing policy for specific service platforms .e.g.video streaming, VOIP, etc. e. Security Control: For security requirement, operators need to take control and identify of certain devices/customers in a quick manner. f. Easy measurement and statistic: The semantic prefix provides explicit identifiers for measurement and statistic. These requirements are largely falling into two categories: some is regarding to the network device features, and the others are related to services provision and subscriber identification. The functional usage of the semantics for the two categories are quite different. Therefore, an ISP semantic IPv6 prefix example is designed as a two- level hierarchical architecture, in which the first level is the function types of prefixes, and the second level is the further usage within an specific prefix type. A.1. Function Type Semantic Bits Function Type (FT): the value of this field is to indicate the functional usage of this prefix. The typical types for operators include network device, subscriber and service platform. +--------+--------+------------------------------------------------+ | | FT | | +--------+--------+------------------------------------------------+ / \ +------------+------------+ |000: network device | |000~010: service platform| |011~101: subscriber | |110: reserved | +-------------------------+ Function Type Bits Example Figure 1 Jiang, et al. Expires January 16, 2014 [Page 16] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 The portion of each type should be estimated according to the actual requirements for operators, in order to use the address space most efficiently. Within the above FT design, the whole ISP IPv6 address space is divided into four parts: the network device address space (1 /8 of total address space), the service platform address space (2/8 of total address space), the subscriber address space (3/8 of total address space), and a reserved address space (1/8 of total address space) for future usage. A.2. Network Device Type Bits within Network Device Address Space Network Device Type (NDT) indicates different types of network devices. Normally, one operator may have multiple networks, e.g.backbone network, mobile network, ISP brokered service network, etc. Using NDT field to indicate specific network within an operator may help to apply some routing policies. Locating NDT bits in the left-most bits means that a single, simple access- control list implemented across all networking devices would be enough to enforce effective traffic segregation. The Locator field is followed behind NDT. +--------+--------+------+-----------------------------------------+ | | FT(000)| NDT | Locator | Network Device bits | +--------+--------+------+-----------------------------------------+ / \ / \ +------------+-----+ |000~001: SubNet 1| |010~110: SubNet 2| |111: Reserved| +------------------+ Network Device Type Bits Example Figure 2 The portion of each subnet type should be estimated according to the actual requirements for operators, in order to use the address space most efficiently. Within the above NDT design, SubNet 1 is assigned 2/8 of the network device address space, SubNet 2 is assigned 5/8, and 1/8 is reserved. A.3. Subscriber Type Bits within Subscriber Address Space Jiang, et al. Expires January 16, 2014 [Page 17] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 Subscriber Type (ST) indicates different types of subscribers, e.g. wireline broadband subscriber, mobile subscriber, enterprise, WiFi, etc. This type of prefix is allocated to end users. Further, division may be taken on subscriber's priorities within a certain subscriber type. The Locator field within subscriber address space is put before ST for better routing aggregation. +--------+--------+---------------+------+-------------------------+ | | FT(011)| Locator | ST | Subscriber bits | +--------+--------+---------------+------+-------------------------+ / \ / \ +----------+------------+---------------+ |0000~0011: broadband access subscriber | |0100~0111: mobile subscriber | |1000~1001: enterprise | |1010~1011: WiFi subscriber | |1100~1111: Reserved | +---------------------------------------+ Subscriber Type Bits Example Figure 3 The portion of each subscriber type should be estimated according to the actual requirements for operators, in order to use the address space most efficiently. Within the above ST design, the broadband access subscriber type is assigned 4/16 of the subscriber address space, the mobile subscriber is assigned 4/16, enterprise type and WiFi subscriber type are assigned 2/16 each, and 2/16 is reserved. A.4. Service Platform Type Bits within Service Platform Address Space Service Platform Type (SPT) indicates typical service platforms offered by operators. This field may have scalability problem since there are numerous types of services . It is recommended that only aggregated service platform types should be defined in this field. This type of prefix is usually allocated to service platforms in operator's data center. +--------+--------+---------------+------+-------------------------+ | | FT(001)| Locator | SPT | Service bits | +--------+--------+---------------+------+-------------------------+ / \ / \ +----------+------------+---------------+ Jiang, et al. Expires January 16, 2014 [Page 18] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 |000~001: Self-running service platform | |001~011: Tenant service platform | |100~101: Independent service platform | |110~111: Reserved | +---------------------------------------+ Service Platform Type Bits Example Figure 4 The portion of each subnet type should be estimated according to the actual requirements for operators, in order to use the address space most efficiently. Appendix B. An Enterprise Semantic Prefix example This enterprise semantic prefix example is also abstracted from an ongoing enterprise address architecture design. This example is designed for a realtime video monitor network across a city region. The semantic prefix solution is planning to be deployed along with a strict authorization system. Note: this example only covers unicast address within IP Version 6 Addressing Architecture [RFC4291]. For this example, the below semantics are important for the network operation and require different network behaviors. a. Terminal type: there are two terminal types only: monitor cameras or video receivers. They are estimated to have similar number. Network devices use another different address space. b. Geographic location: the city has been managed in a three-level hierarchical regionalism: district, area and street. Each level has less than 28 sub-regions. This can also be considered as a replacement of topology locator within this specific network. c. Authorization level: the network operator is planning to administrate the authorization in three or four levels. An receiver can access the cameras that are the same or lower authorization level. d. Civilian or police/government. e. Device attribute: this indicates the attribute of a camera device. The attribute is expressed in an abstract way, such as road traffic, hospital, nursery, bank, airport, etc. The abstracted attribute type is designed to be less than 64. Jiang, et al. Expires January 16, 2014 [Page 19] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 f. Receiver Attribute: this indicates the attribute of a video receiver. The attribute is based on the receiver group, such as police, firefighter, local security, etc. The attribute/receiver group type is designed to be less than 128. This example enterprise network has obtained a /32 address block from ISP. There is another /48 dedicated for network devices. The first bit is Terminal type, which indicates terminal type. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ISP assigned block | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |T| Geographic Locator | AL|C|Device Attr| Device Bit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ A semantic prefix design example for cameras Figure 5 3-level hierarchical geographic locator takes 15 bits (each level 5 bits, 32 sub-regions). Authorization level takes 2 bits and 1 bit differentiates civilian or police/government. 6 bits is assigned for device attribute. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ISP assigned block | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |T| GeoLoc | AL|C|Receiver Attr| Topology Locator |ReceiverBit| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ An semantic prefix design example for video receivers Figure 6 The receiver is not as much as geographically distributed as cameras. Therefore, Geographic locator is only detailed to district level. Topology locator is needed for network forwarding and aggregation within a district. It is assigned 10 bits. Authorization level bits and civilian bit are the same with camera address space. Receive attribute takes 7 bits, giving it is designed to be up to 128. Appendix C. A Multi-Prefix Semantic example A multiple-site enterprise may have been assigned several prefixes of different lengths by its upstream ISPs. In this situation, in order Jiang, et al. Expires January 16, 2014 [Page 20] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 to create a single, contiguous Semantic Prefix Domain, it is necessary to base the semantic prefix policy on the longest assigned prefix to ensure that there in enough addressing space to encode a consistent set of semantics across all of the assigned prefixes. In this example, an enterprise has received a /38 address block for one site (A) and a /44 for a second site (B) . They can be organized in the same Semantic Prefix Domain. The most-left 18 (site A) and 12 (site B) bits are allocated as locator. It provides topology based network aggregation. The 8 right-most bits (from bits 56 to 63) are assigned as the semantic field. In this design, the multiple-site enterprise that has been assigned two prefixes of different lengths can be organized as the same Semantic Prefix Domain. The semantic and the Semantic Prefix Domain can traverse the intermediate ISP networks, or even public networks. The similar situation may happen on ISPs in the future, when an ISP used up its assigned address space, or built up multiple networks in different places. Authors' Addresses Sheng Jiang (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 BeiQing Road Hai-Dian District, Beijing 100095 P.R. China Email: firstname.lastname@example.org Qiong Sun China Telecom Room 708, No.118, Xizhimennei Street Beijing 100084 P.R. China Email: email@example.com Ian Farrer Deutsche Telekom AG Bonn 53227 Germany Email: firstname.lastname@example.org Jiang, et al. Expires January 16, 2014 [Page 21] Internet-Draft Semantic IPv6 Prefix Analysis July 2013 Yang Bo Huawei Technologies Co., Ltd Q21, Huawei Campus, No.156 BeiQing Road Hai-Dian District, Beijing 100095 P.R. China Email: email@example.com Tianle Yang China Mobile 32, Xuanwumenxi Ave. Xicheng District Beijing 100053 China Email: firstname.lastname@example.org Jiang, et al. Expires January 16, 2014 [Page 22]